Vol.3, No.5, 663-668 (2012) Agricultural Sciences
Influence of different levels of humic acid and
esterified glucomannan on growth performance
and intestinal morphology of broiler chickens
Seyed Mozafar S. M. Taklimi1, Hassan Ghahri2, Mohammad Asadi Isakan1
1Department of Animal Physiology and Nutrition, Animal Science Research Institute, Karaj, Iran;
*Corresponding Author: seyedmozafar@yahoo.com, seyedmozafar@gmail.com
2Urmia Branch Islamik Azad University, Urmia, Iran
Received 25 January 2012; revised 7 March 2012; accepted 2 May 2012
A s tudy was under taken to investigate the effe ct
of dietary supplementations of humic acid and
esterified glucomannan on broiler performance
and the morphological measurements of small
intestine. Two hundred and ten-day-old broiler
chicks were weighed and randomly assigned to
seven treatment groups in triplicate. The dietary
treatments included (T1) control (basal diet
without any additives), (T2) basal diets supple-
mented with 0.1% humic acid, (T3) basal diets
supplemented with 0.2% humic acid, (T4) basal
diets supplemented with 0.3% humic acid, (T5)
basal diets supplemented with 0.1% esterified
glucomannan, (T6) basal diets supplemented
with 0.2% esterified glucomannan and (T7) basal
diets supplemented with 0.3% esterified gluco-
mannan. Different parameters including body
weight gain (BWG), feed intake (FI), feed con-
version ratio (FCR) and morphology of small in-
testine were evaluated during six weeks of ex-
perimental period. According to the results, at
the end of experimental period, the highest av-
erage BWG were recorded in T4 group (fed with
0.3% humic acid), compared to control (T1) and
other experimental groups (p < 0.05). Whereas,
the highest body weight gain were observed
during starter period in treatment 7 (fed with
0.3% esterified glucomannan) as compare to
other experiment al groups (p < 0.05). S t atistically,
feed intake remained unaffected during the ex-
perimental period in all the treatment groups.
However, the lowest and the highest feed intake
were observed numerically within treatments T4
and T1 with 4229.70 g and 4362.30 g, respec-
tively. Addition of dietary supplements used in
the study appeared to have significant effect on
the morphology of the small intestine (jejunum
mucosal development) of the broilers in differ-
ent tre a t m e n t g r o u ps. C om par ed t o c o n tr o l group,
the inclusion of either humic acid or esterified
glucomannon decreased (p < 0.01) the crypt
depth and increased villus height respectively
(p < 0.05). Moreover, the diet supplements with
humic acid 0.3% (T4) decreased crypt depth
compared to esterified glucomannan and con-
trol. The dietary supplementations resulted in an
increase in the villus height of intestinal mucosa
of broilers. The increase in the villus height was
associated with improvement of growth perfor-
mance for both humic acid and esterified glu-
comannan. Based on our result s it appeared that
humic acid and esterified glucomannan can be
used as a growth promoter in broiler diets and
they can improve the gut health too.
Keywords: Broiler Chicks; Humic Acid; Esterified
Glucomannan; Small Intestine
Any attribute which can improve gastrointestinal tract
health and immunity is extremely valuable in broiler
diets. In last decades antibiotics had been used widely
world-wide in poultry industry in order to prevent poul-
try pathogens and disease and to improve meat and egg
production. However, with the unavoidable spread of
bacterial resistance and cross resistance the use of antibi-
otics has been considered hazardous [1-3]. As conse-
quences, many alternatives have been discussed includ-
ing probiotics, prebiotics, herbal compounds and organic
acids. Most of these substances exert their effects by in-
fluencing gastrointestinal flora and digestion processes.
Among these alternatives the influence of humic acid has
been studied extensively, and has been reported to have
Copyright © 2012 SciRes. OPEN ACCESS
S. M. S. M. Taklimi et al. / Agricultural Sciences 3 (2012) 663-668
positive impact on the growth performance of birds.
Humic acid defined as a class of compounds resulting
from decomposition of organic matter, particularly plants
are natural constituents of drinking water, soil and lignite.
Humic acid inhibit bacterial and fungal growth, thus de-
crease levels of mycotoxins in feed [4,5]. Beneficial ef-
fects of humic acid are described concerning stress ma-
nagement [6], immune system [7,8], anti-inflammatory
activity [9], antiviral properties [10], as well as preven-
tion of intestinal diseases, mainly diarrhea in humans and
animals. There are also reports that routine use of humic
acid in the feed has a positive influence on growth of
broilers [11,12]. The beneficial effect of humic acid on
growth in different species of animals has been consid-
ered its capacity of changing gut physiology and inter-
ference in immunity [13]. Beside humic acid, yeast and
yeast cultures have a long standing tradition of use in
animal feeds. Yeast culture has been shown to affect in-
testinal mucosa development in poultry. In addition to
growth performance, there are many trials showing that
enrichment of diets with yeast could favorably improve
the quality of edible meat from broilers. Yeast is also an
excellent source of selenium and chromium; two trace
minerals which may have positive effects of broiler
health [14]. Since, 80’s decades Oligosaccharide from
outer cell wall component of live yeast (Saccharomyces
cerevisiae), were introduced as a feed additive commer-
cially in poultry industry. Since then, many studies have
been conducted to investigate the effects of esterified
glucomannan or it’s derivatives on various parameters
such as body weight, feed conversion ratio and feed in-
take of birds [15-17]. The objective of this study was to
determine if experimental supplementation of different
level of humic acid and esterified glucomannan in the
young broiler chicken diet may improve performance
and small intestine mucosal development of broiler
2.1. Birds and Experimental Design
Two hundred and ten-day old (mixed sex) commercial
Ross broiler chicks were randomly subjected to seven
different treatment groups (three replicates of 10 chicks
per dietary treatment). All birds were weighed (initial
weight) individually after their arrival from the hatchery
to the experimental farm, and on completion of the ex-
periment day 42. The experiment was designed com-
pletely randomized to evaluate the effect of two different
naturally available feed additives humic acid (FH =
Farmagu lator D RYTM humate Yayalar Mah. Sanayi Cad.
No. 29, Dolayoba, Pendik, Istanbul, Tu rkey ), and esteri-
fied glucomannan, (Bio-Mos, USA) on small intestine
mucosal development of digestive tract of birds. The
birds were fed one of seven experimental treatments for
42 days. The experimental diets were as follows: T1 =
Control (basal diet + no feed additives). T2 = T1 + 0.1%,
T3 = T1+ 0.2% and T4 = T1+ 0.3% humic acid and T5 =
T1 + 0.1%, T6 = T1 + 0.2% and T7 = T1 + 0.3% esteri-
fied glucomannan, respectively.
2.2. Performance
All chicks were reared under uniform management
conditions with feed and water available ad libitum. In-
dividual body weight gain (BWG), feed intake (FI), feed
conversion ratio (FCR) of the birds were recorded at the
onset of experiments and measured daily thereafter for
each group.
2.3. Small Intestine Mucosal Development
To study the mucosal development of small intestine
of the chicks at the end of experimental period, 3 birds
were selected randomly from each replicate and sacri-
ficed and their histomorphology studied.
Gut morphology (jejunum) examinations were carried
out according to the method which was described [18].
Jejunum samples were immersed in 4% formalin for 48
hrs. The processing consisted of serial dehydration, clear-
ing, and impregnation with wax. Tissue sample was sec-
tioned at a thickness of 7 - 8 μm, were cut by a micro-
tome and were fixed on slides. A routine staining proce-
dure was carried out using hematoxylin and eosin. The
slides were viewed on a microscope. Visual observations
of villus height, crypt depth were made at 10.25× magni-
fication under an IMI microscope.
2.4. Statistics
All data were statistically analyzed by ANOVA using
the SAS system [19]. Significant differences between the
treatment means were compared by using Duncan Multi-
ple Range test [20].
The statistical model used was
Yij = µ + Ti + eij
Yij = observation in block i and treatment j, µ = Over-
all sample mean, Ti = Effect of treatment i, eij = Error.
The effect of different levels of humic acid and esteri-
fied glucomannan on body weight gain of broilers during
the experimental period is shown in Table 1. A sig-
nificant increase in BWG was recorded in birds which
was fed with either humic acid or esterified glucomannan
(p < 0.05). According to the results, birds fed with 0.3%
Copyright © 2012 SciRes. OPEN ACCESS
S. M. S. M. Taklimi et al. / Agricultural Sciences 3 (2012) 663-668 665
Table 1. Effects of humic acid and esterified glucomannan on
mean BWG (g) of Broiler.
0 - 42 days21 - 42 days 0 - 21 days Treatments
2147.00b 1459.67b 687.33c T1 (control)
1554.67bc 712.67bc T2 (0.1% Humic acid)
2337.67a 1611.33a 726.33abc T3 (0.2% Humic acid)
2373.67a 1650.33a 723.33abc T4 (0.3% Humic acid)
1551.00ab 726.67abc T5 (0.1% Live yeast)
2363.33a 1622.67a 740.67ab T6 (0.2% Live yeast)
2331.67a 1602.00a 763.00a T7 (0.3% Live yeast)
* * *
*Mean bears not common superscript are different significantly (p < 0.05).
a,b,cmeans: Values in the table shows with different superscripts are signifi-
cantly different (p < 0.05).
estrified glucomannan performed well at the early age,
while with advancing age, humic acid had an increasing
effect on overall performance of the birds. The highest
and the lowest BWG was observed in T7 and T1 (763.00
vs 687.33 g) during their initial growing phase (0 - 21
days), respectively, while, chicks in T4 (0.3% humic acid)
gained more body weight during the 2nd phase of growth
(21 - 42 days) as well during the whole experimental
period (p < 0.05).
As Table 2 indicates, feed intakes were not affected
significantly by inclusions of different levels of either
humic acid or esterified glucomannan in diets, during the
experimental period. However, feed conversion ratio of
the chicks in different treatment groups were signifi-
cantly different with the presence of either humic acid or
esterified glucomannan. According to the results pre-
sented in Ta b l e 3, the highest feed conversion ratio was
observed in T4 (1.781), as compared to other experimen-
tal groups (p < 0.01). Overall results indicated that, birds
fed diets with humic acid (0.3%) had higher mean live
weight gain, low feed intake and better feed conversion
Table 4 indicated that, feed additives used in this
study had significantly effect on the villus height (p <
0.05) of broiler chicks (Figure 1). All levels of humic
acid and esterified glucomannan used had the ability to
increase crypt depth (p < 0.01). Where as, highest crypt
depth were observed in T7, compared to other treatments.
As evidence shows that, effects of humic acid and esteri-
fied glucomannan, is proposed to be due to their contents
of anti bacterial agents and enhancement of multiplica-
tions of beneficial macroscopic bacteria and elimination
of harmful bacteria in bird's digestive tract.
According to the results of this experiment, humic acid
Table 2. Effects of humic acid and esterified glucomannan on
FI (g) of Broiler.
0 - 42 days21 - 42 days 0 - 21 days Treatments
4362.30 3274.30 1088.00 T1 (control)
4295.00 3217.30 1077.67 T2 (0.1% Humic acid)
4285.70 3253.00 1032.67 T3 (0.2% Humic acid)
4229.70 3172.00 1057.67 T4 (0.3% Humic acid)
4274.30 3217.30 1042.00 T5 (0.1% Live yeast)
4317.00 3257.00 1060.00 T6 (0.2% Live yeast)
4327.70 3265.70 1062.00 T7 (0.3% Live yeast)
ns ns ns
ns = Not significantly different (p < 0.05).
Table 3. Effects of humic acid and esterified glucomannan on
mean FCR.
0 - 42 days21 - 42 days 0 - 21 days Treatments
2.031a 2.243a 1.583a T1 (control)
1.894b 2.069b 1.512ab T2 (0.1% Humic acid)
1.833c 2.018bc 1.421b T3 (0.2% Humic acid)
1.781d 1.922c 1.462ab T4 (0.3% Humic acid)
1.876c 2.074b 1.433b T5 (0.1% Live yeast)
1.826c 2.00bc 1.431b T6 (0.2% Live yeast)
1.856c 2.038b 1.392ab T7 (0.3% Live yeast)
** *
*Mean bears not common superscript are different significantly (p < 0.05);
**Mean bears not common superscript are different significantly (p < 0.01).
a,b,cmeans: Values in the table shows with different superscripts are signifi-
cantly different (p < 0.05).
Table 4. Effects of humic acid and esterified glucomannan on
Jejunum mucosal development of broiler.
Crypt depth (mm)Length of villiae (mm) Treatments
2.243a 1.026b T1 (control)
2.069b 1.290ab T2 (0.1% Humic acid)
2.018bc 1.383a T3 (0.2% Humic acid)
1.922c 1.340a T4 (0.3% Humic acid)
2.074b 1.260ab T5 (0.1% Live yeast)
2.00bc 1.293ab T6 (0.2% Live yeast)
2.038b 1.246b T7 (0.3% Live yeast)
** *
*Mean bears not common superscript are different significantly (p < 0.05);
**Mean bears not common superscript are different significantly (p < 0.01).
a,b,cmeans: Values in the table shows with different superscripts are signifi-
cantly different (p < 0.05).
Copyright © 2012 SciRes. OPEN ACCESS
S. M. S. M. Taklimi et al. / Agricultural Sciences 3 (2012) 663-668
Copyright © 2012 SciRes.
Figure 1. Vertical view of small intestine (jejunum, depth of crypt and length of villae, 100× magnifications).
and esterified glucomannan added as supplement in the
feed had significantly effect on the performance of birds.
This is in general agreement with a number of recent
reports [14,12,21,22]. Nevertheless, Humic acid had
higher effects on birds as compare to esterified gluco-
mannan by means of 1) Ability to create protective layers
over the epithelial mucosal membrane of digestive tract
against the penetrations of toxic and other bacterial con-
taminated substances; 2) Will have ability to increase
metabolism of protein and microbial carbohydrates based
on catalyzing agents by bringing down the pH of small
intestine; 3) It acts as detoxification agents in intestine
(due to reducing power in absorption of nitrates, fluorites
and heavy metals); 4) To increase immune receptors in
digestive tract over preserving the beneficial pathogens
[23]. There is some evidence that shows, by inclusions of
esterified glucomannan in feed will increase bird’s
growth through reducing the harmful gut micro phlora by
de-colonizing salmonella like bacteria, will increase
bird’s body weight, immune system, nutrient digestibility
and gut health due to its effect on substituting harmful
with beneficial gut micro phlora [17]. Esterified gluco-
mannan will also shows its beneficial effect on birds
through challenge with some un-expected growth inhibi-
tors like aflatoxin, coccodiosis, heat stress and poor feed
quality [17]. Feed intake was also affected numerically
by inclusions of humic acid or esterified glucomannan at
different levels throughout the experimental periods.
Birds had offered diets containing 0.3% humic acid had
lower levels of feed intake as compare to other experi-
mental groups. This finding was in accordance with the
reports of [21,22]. Feed conversion ratio was affected by
inclusions of humic acid and esterified glucomannan
throughout the experimental period. Best feed conversion
ratio was observed in 0.3% humic acid supplemented
groups, and it was in accordance with the reports of
[12,14]. It is assumed that, due to the chemical composi-
tions like, proteins, water soluble vitamins, digestive
enzyme and many other immune stimulating agent and
antibacterial substances in humic acid and in esterified
glucomannan, they will have significant role in the of
health and productivity of birds. This could be mainly
attributed to their ability to change the gut micro flora
(by increasing the concentrations of beneficial bacteria)
in the intestine [24-26]. In the present study, inclusion of
0.3% humic acid in broiler diets had significantly better
effects on bird performance. As reported earlier by
[27,28], humic acid and esterified glucomannan had sig-
nificant effect on crypt depth of villiae in Jejunum of
treated birds compared to non supplemented groups. It is
obviously known that, growth of villiae will be depend-
ing on pH, micro flora and toxic substances in the intes-
S. M. S. M. Taklimi et al. / Agricultural Sciences 3 (2012) 663-668 667
tine. Though, humic acid will have the ability in reducing
pH and concentration of harmful bacteria in intestine.
There is evidence that humic acid could have positive
effect on animal performances via digestive tract ecosys-
tems [29]. Esterified glucomannan at higher dosage will
increase height of villiae and crypt depth and inhalations
of damaged villiae [30]. It also will secrete more en-
zymes in taller (projected) villiae, which finally will en-
hance the absorption and digestion of food particles.
Moreover, esterified glucomannan will have effect to
create protective layers on intestinal mucus, to inhibit
penetrations of toxic substances and harmful bacteria in
the gut.
To conclude, humic acid or esterified glucomannan
displayed a greater efficacy as growth promoters for broil-
ers and could be a suitable substitution as an alternative
for antibiotics.
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